The present invention relates generally to a stack package, and more particularly, to a stack package which can substantially prevent the occurrence of cracks due to a difference in coefficient of thermal expansion between component parts.
Recently, a semiconductor package having a memory semiconductor chip capable of storing and processing a huge amount of data within a short time has been developed. Also, a stack package has been developed, in which a plurality of memory semiconductor chips are stacked at a chip level or a package level to increase data storage capacity. A package-on-package (POP) is a representative example of a stack package which is constructed by stacking memory semiconductor chips at a package level.
Further recent developments include a system-in-package (SIP), in which memory semiconductor chips and a system semiconductor chip are stacked to improve data storage capacity and data processing speed. Typically, such a system-in-package is constructed by stacking the memory semiconductor chips and the system semiconductor chip at a chip level. As the case may be, the system-in-package may be constructed by stacking the memory semiconductor chips and the system semiconductor chip at a package level.
Conventional stack packages are constructed by vertically stacking semiconductor packages. However such vertically stacked semiconductor packages are problematic because cracks can occur due to a difference in coefficient of thermal expansion between component parts, thus reducing the reliability of such packages.
In detail, in the conventional stack packages, an electrical connection between a first package and a second package is accomplished by forming pre-solders or copper posts in the first package. In such a conventional stack package structure, due to a mismatch in coefficient of thermal expansion (CTE) between an epoxy molding compound (EMC) provided as an encapsulation member for sealing a semiconductor chip, and the pre-solders or the copper posts formed in the first package for electrical connection between the first package and the second package, warpage and cracks can occur in the first package, whereby the reliability of the stack packages can be degraded.